CRISPR-Cas9 technology has greatly improved our ability to target and mutate specific DNA sequences, revolutionizing mutagenesis in many model organisms. There has been recent interest in creating CRISPR guide RNA (gRNA) libraries containing complex mixtures of gRNAs targeting large sets of genes, including comprehensive sets targeting the entire genome. However, because each targeting region must be individually synthesized, these libraries are very expensive to generate. Therefore, the development of rapid, inexpensive methods for creating CRISPR gRNA libraries is desirable. In order to address the costs associated with library development, PCT Patent Application Publication No. WO 2016/196805, which is incorporated in its entirety by reference herein, discloses methods for enzymatically generating CRISPR gRNA libraries. The disclosed methods involve restriction digest of a double stranded DNA starting set created from genomic DNA, PCR products, or RNA and followed by a complex set of adapter ligations and removals with extensive wash steps in between. The complete protocol as disclosed contains over 20 steps, requires several expensive kits and enzymes, and takes at least three days to complete (or approximately twelve hours plus a required overnight incubation). Due to the complex nature of the protocol, it is also hindered by low yields and frequent failures.